1. Field of the Invention
This invention relates to a new expansion joint for use in preparing concrete products. More particularly, the invention relates to a new type of expansion joint for concrete products that is self supporting and greatly facilitates the preparation of the concrete product.
Specifically, the invention provides a new type of expansion joint for concrete products that is self-supporting, gives a clean straight line and facilitates the screeding process. The new expansion joint broadly comprises a single unit plastic molded inverted T having a flat base adapted to resting on the ground and a vertical beam perpendicularly joined to the center of said base, said beam being thicker at the point of junction with the base than at the top of said base, the plastic used in the molding of at least a portion of said beam being prepared from a plastic material that compresses and expands on temperature change.
As a special embodiment, the invention further provides an expansion joint as described above wherein the center core of the said beam is filled with or prepared from a material which is more expandable and compressible than the material used for preparing the other portion of the expansion joint.
The invention further provides a method for using the above-noted expansion joints to produce improved concrete products. 2. Prior Art
As is well known, concrete products, such as roadways, sidewalks, etc., expand and contract on change of temperature, and this in many case causes the concrete to crack and break up. To avoid the problem, it is general policy in the construction business to introduce expansion joints at frequent locations in the product to absorb the expansion or contraction without breaking the concrete. Todate, these expansion joints have been prepared by utilizing board separators at frequent intervals during the pouring and then when the concrete begins to set up to remove the boards and introduce in their place a strip of soft expandable material.
The use of such expansion joints has not been entirely satisfactory. The addition of the board separators and their later removal is a time consuming and messy operation. In many cases, for example, the removal of the separator board is difficult and leaves an uneven and crooked dividing line in the finished product. Furthermore, the soft material inserted in the place of the board separator is easily worn and removed on subsequent use of the concrete product, and this leaves an unsightly and defective product. In addition, these problems are multiplied when one attempts to use such separators to form expansion joints in a curved or other artistically designed pattern.
It is an object of the invention, therefore, to provide a new type of expansion joint that solves the abovedescribed problems. It is a further object to provide an expansion joint that is self supporting and remains in the concrete product and does not have to be removed. It is a further object to provide a new type of expansion joint that insures a straight and clean line along the dividing line in the cured concrete product. It is a further object to provide an expansion joint that greatly facilities the screeding during the finishing of the concrete product. It is a further object to provide an expansion joint that can be easily used to form curved or other types of artistically desired patterns for the said expansion joint. In addition, it is a further object to provide new expansion joints that are economical to use and reduce the cost of the formation of concrete products, such as highways, runways, sidewalks, driveways, and the like. These and other objects will be apparent from the following detailed description thereof.